1. Field of the Invention
Embodiments of the invention generally relate to a load lock chamber for a vacuum processing system, and more specifically, to a heated load lock chamber.
2. Description of the Related Art
Two rapidly evolving technology areas are thin film transistors and photovoltaic devices. Thin film transistors (TFT) formed by flat panel technology are commonly used for active matrix displays such as computer and television monitors, cell phone displays, personal digital assistants (PDAs), and an increasing number of other devices. Generally, flat panels comprise two glass plates having a layer of liquid crystal materials sandwiched therebetween. At least one of the glass plates includes one conductive film disposed thereon that is coupled to a power source. Power, supplied to the conductive film from the power source, changes the orientation of the crystal material, creating a pattern display.
Photovoltaic devices (PV) or solar cells are devices which convert sunlight into direct current (DC) electrical power. PV or solar cells typically have one or more p-n junctions formed on a panel. Each junction comprises two different regions within a semiconductor material where one side is denoted as the p-type region and the other as the n-type region. When the p-n junction of the PV cell is exposed to sunlight (consisting of energy from photons), the sunlight is directly converted to electricity through the PV effect. In general, a high quality silicon-based material is desired to produce high efficiency junction devices (i.e., high power output per unit area). Amorphous silicon (a-Si) film has been widely used as the silicon-based panel material in PV solar cells due to its low cost to manufacture in conventional low temperature plasma enhanced chemical vapor deposition (PECVD) processes.
With the marketplace's acceptance of flat panel technology and desire for more efficient PV devices to offset spiraling energy costs, the demand for larger panels, increased production rates and lower manufacturing costs have driven equipment manufacturers to develop new systems that accommodate larger size substrates for flat panel display and PV device fabricators. Current substrate processing equipment is generally configured to accommodate substrates slightly greater than about two square meters. Processing equipment configured to accommodate larger substrate sizes is envisioned in the immediate future.
Equipment to fabricate such large substrates represents a substantial investment to fabricators. Conventional systems require large and expensive hardware. In order to offset this investment, high substrate throughput is very desirable.
Heating and/or cooling of the substrate within the load lock chamber is an important aspect for achieving high system throughput. As future processing systems are envisioned to process even larger size substrates, the need for uniform rapid heating and cooling of large area substrates is of great concern. In particular, the deflection due to the large surface area exposed to vacuum presents a challenge in maintaining uniform spacing between the heaters, substrate and chamber body. Moreover, as electrical connections for conventional resistive heaters and lamp utilized to heat substrates within the load lock chambers are exposed to vacuum, the connections are subject to arcing which may damage the chamber hardware and/or generate particles which then become a source of unwanted contamination. As such, advancements which promote uniform temperature regulation, hardware longevity, contamination control and high heat transfer rates are highly desirable.
Thus, there is a need for an improved load lock chamber that facilitates rapid and uniform heating and cooling of larger area substrates.